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Create the concept of 'owned data' in upb/rust as a generalization of…
… the upb.rs SerializedData (which is a arena + data for arbitrary types, both thin and wide ref types), use that for the wire parse/serialize path. PiperOrigin-RevId: 626012269
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,111 @@ | ||
| use crate::Arena; | ||
| use std::fmt::{self, Debug}; | ||
| use std::ops::{Deref, DerefMut}; | ||
| use std::ptr::NonNull; | ||
|
|
||
| /// An 'owned' T, similar to a Box<T> where the T is data | ||
| /// held in a upb Arena. By holding the data pointer and a corresponding arena | ||
| /// together the data liveness is be maintained. | ||
| /// | ||
| /// This struct is conceptually self-referential, where `data` points at memory | ||
| /// inside `arena`. This avoids typical concerns of self-referential data | ||
| /// structures because `arena` modifications (other than drop) will never | ||
| /// invalidate `data`, and `data` and `arena` are both behind indirections which | ||
| /// avoids any concern with std::mem::swap. | ||
| pub struct OwnedArenaBox<T: ?Sized + 'static> { | ||
| data: NonNull<T>, | ||
| arena: Arena, | ||
| } | ||
|
|
||
| impl<T: ?Sized + 'static> OwnedArenaBox<T> { | ||
| /// Construct `OwnedArenaBox` from raw pointers and its owning arena. | ||
| /// | ||
| /// # Safety | ||
| /// - `data` must satisfy the safety constraints of pointer::as_mut::<'a>() | ||
| /// where 'a is the passed arena's lifetime (`data` should be valid and | ||
| /// not mutated while this struct is live). | ||
| /// - `data` should be a pointer into a block from a previous allocation on | ||
| /// `arena`, or to another arena fused to it, or should be pointing at | ||
| /// 'static data (and if it is pointing at any struct like upb_Message, | ||
| /// all data transitively reachable should similarly be kept live by | ||
| /// `arena` or be 'static). | ||
| pub unsafe fn new(data: NonNull<T>, arena: Arena) -> Self { | ||
| OwnedArenaBox { arena, data } | ||
| } | ||
|
|
||
| pub fn data(&self) -> *const T { | ||
| self.data.as_ptr() | ||
| } | ||
|
|
||
| pub fn into_parts(self) -> (NonNull<T>, Arena) { | ||
| (self.data, self.arena) | ||
| } | ||
| } | ||
|
|
||
| impl<T: ?Sized + 'static> Deref for OwnedArenaBox<T> { | ||
| type Target = T; | ||
| fn deref(&self) -> &Self::Target { | ||
| self.as_ref() | ||
| } | ||
| } | ||
|
|
||
| impl<T: ?Sized + 'static> DerefMut for OwnedArenaBox<T> { | ||
| fn deref_mut(&mut self) -> &mut Self::Target { | ||
| self.as_mut() | ||
| } | ||
| } | ||
|
|
||
| impl<T: ?Sized + 'static> AsRef<T> for OwnedArenaBox<T> { | ||
| fn as_ref(&self) -> &T { | ||
| // SAFETY: | ||
| // - `data` is valid under the conditions set on ::new(). | ||
| unsafe { self.data.as_ref() } | ||
| } | ||
| } | ||
|
|
||
| impl<T: ?Sized + 'static> AsMut<T> for OwnedArenaBox<T> { | ||
| fn as_mut(&mut self) -> &mut T { | ||
| // SAFETY: | ||
| // - `data` is valid under the conditions set on ::new(). | ||
| unsafe { self.data.as_mut() } | ||
| } | ||
| } | ||
|
|
||
| impl<T: Debug + 'static> Debug for OwnedArenaBox<T> { | ||
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | ||
| f.debug_tuple("OwnedArenaBox").field(self.deref()).finish() | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
| use std::str; | ||
|
|
||
| #[test] | ||
| fn test_byte_slice_pointer_roundtrip() { | ||
| let arena = Arena::new(); | ||
| let original_data: &'static [u8] = b"Hello world"; | ||
| let owned_data = unsafe { OwnedArenaBox::new(original_data.into(), arena) }; | ||
| assert_eq!(&*owned_data, b"Hello world"); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_alloc_str_roundtrip() { | ||
| let arena = Arena::new(); | ||
| let s: &str = "Hello"; | ||
| let arena_alloc_str: NonNull<str> = arena.copy_str_in(s).into(); | ||
| let owned_data = unsafe { OwnedArenaBox::new(arena_alloc_str, arena) }; | ||
| assert_eq!(&*owned_data, s); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_sized_type_roundtrip() { | ||
| let arena = Arena::new(); | ||
| let arena_alloc_u32: NonNull<u32> = arena.copy_in(&7u32).into(); | ||
| let mut owned_data = unsafe { OwnedArenaBox::new(arena_alloc_u32, arena) }; | ||
| assert_eq!(*owned_data, 7); | ||
| *owned_data = 8; | ||
| assert_eq!(*owned_data, 8); | ||
| } | ||
| } |
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